how do I create an international ngo (being German and living in Chile)?

In these days, everybody can start an "international NGO". Since there
is no "World Law" yet, you are bond to the country you are living in.
The term "international" does ony refer to its importance. If a
national NGO begins cause significant impact in a political debate, it
will get a chance to get involved in international activities. This is
first informal and based on personal effort. Some UN-Organisations are
providing national NGOs the opportunity in getting part in a debate
but we're talking about things *everybody* who needs to know knows. I
don't want to disappoint you but it seems that you have a long way
ahead.

Maybe the Chilenian Codico Civil contians some hints :)
http://www.netchile.com/normas/codice/codigocivil.html